218 
wardly curved terminal process. The inner mar- 
gin of the third segment is broken by the lobe- 
shaped proximal region. The division between 
the terminal process and the segment is indis- 
tinct. In addition to the terminal process, a 
small seta-like accessory process is present on 
the lobate inner proximal region. 
The second antenna of the third chalimus 
(Fig. 15g) appears to have degenerated even 
more when compared with the same appendage 
on the copepodite and the previous two chal- 
imus stages. This condition is a continuation of 
the trend initiated in the first chalimus, a grad- 
ual loss of rigidity and distinct form before the 
development of the adult appendage. To ex- 
emplify this loss of form, the segments of the 
third chalimus appendage are distinct but plastic 
in nature, the integument is flabby, and the 
ridges and grooves present on the second an- 
tenna of one side of a specimen are often absent 
on the other; further, the sclerotization of the 
terminal process appears reduced. The greatest 
length and width of the first and second seg- 
ments of the second antenna of the third chal- 
imus are approximately equal although the shape 
is different. The distal end of the first segment 
is generally concave, of the second segment al- 
most flat. The third segment is slightly shorter 
than either of the preceding two and is tapered 
from the broad proximal to pointed distal end. 
The inner margin of the segment possesses a 
distinct protrusion on the distal one-half that 
is tipped by a short, pointed process. The more 
heavily sclerotized terminal process of the suc- 
ceeding stage is visible inside the distal portion 
of the third segment. 
The second antenna of the fourth chalimus 
(Fig. 15 h) is similar in general make-up to that 
of the preceding stage except that the first seg- 
ment is not as long. Further, it has a flaplike 
structure projecting distally from the proximal 
end; one specimen also possessed a triangular, 
distally directed flap that appeared to correspond 
to the posteriorly directed, pointed process on 
the first segment of the adult female. The length 
of the second segment is greater than that of 
the first, the division between the second and 
third segments is indistinct, and the lateral mar- 
gins of both segments are irregular. The distal 
inner margin of the third segment bears a small, 
lobate process that will become the accessory 
PACIFIC SCIENCE, Vol. XVII, April 1963 
process of the adult and is the protrusion that 
was present on the same region of the previous 
stage. The distal end is bluntly pointed, more 
heavily sclerotized than the preceding stage but 
not as heavily as the terminal process of the fifth 
chalimus, visible inside the fourth. 
The second antenna of the female and male 
fifth chalimus (Fig. 15 i) are similar. The gen- 
eral appearance of the adult female appendage 
is now beginning to manifest itself in the fe- 
males of this stage. The first segment is irregu- 
lar, the distal surface concave and forming the 
articulation surface for the second segment. A 
spinelike, posteriorly directed process is present 
on the posterior surface of the segment. The 
second segment is short and strongly developed; 
the inner margin is convex, approximately 3 
times the length of the concave outer margin 
due to the angled distal and proximal surfaces. 
The distal surface of the second segment is ir- 
regular; the inner portion is concave, the outer 
convex although both portions are heavily scle- 
rotized and form the articulation surface for 
the third segment. The third segment and ter- 
minal process in both sexes is approximately 
IVi times the length of the second segment; 
the proximal surface is lobate and articulates in 
the concavity of the distal end of the second 
segment. The terminal process of the third seg- 
ment is curved inwards strongly at the distal 
end; the division between the process and the 
segment is indistinct. Further, two seta-like ac- 
cessory processes are now present, one on the 
posterior proximal region, the second on the 
inner distal region. 
The second antenna of the sixth chalimus 
(Fig. 15;, k) is similar in both sexes. The first 
segment is slightly longer in the male but, for 
both male and female, is short and the entire 
distal surface is concave, forming an articulation 
surface for the second segment. The first seg- 
ment is irregular in outline, the outer surface 
appearing platelike and tapered gradually to the 
distal surface, the inner surface somewhat ir- 
regular, with a posteriorly directed, spinelike 
projection that is more distinct than in the pre- 
vious stage. The second segment is strongly de- 
veloped, its greatest width slightly more than 
four-fifths of the greatest length; the outer mar- 
gin is flatly convex, longer than the irregularly 
concave inner margin. The width of the distal 
